Facsimile apparatus



- Sept. 19, 1944. c. J. YOUNG FACSIMILE APPARATUS Filed Dec. 24, 1941 2Sheets-Sheet l INVEINTOR fiar FZZJJG A'iTORNEY Patented Sept. :19, 1944UNITED STATE rscsmmn s'rrmrus Charles J. Young. Ardmore, 2a., assignmtoRadio Corporation of America, a corporation of Delaware ApplicationDecember 24, 1941, Serial No. 424,275

(Claims.

the transmission and reproduction of intelligence,

and more particularly to the transmission and reproduction offacsimiles.

The art of facsimile transmission and reception has been developed to ahigh degree, and is be ing found particularly useful at the present timefor the transmission of messages by so-called tape type of facsimilewherein the intelligence to be transmitted is recorded on acomparatively narrow tape, in contradistinction to the normal facsimiletransmissions wherein a comparatively large sheet is used in the natureof a photograph or the like. Accordingly, it is one of the objects of myinvention to provide an apparatus which will be particularly useful forthe transmission and reception of optical images recorded on acomparatively narrow tape.

One of the disadvantages attendant the transmission of facsimiles of thetape type is the fact that the average scanning arrangement is too bulkyand is .not adaptable for this problem, but special scanningarrangements must be utilized. Accordingly, it is another of the objectsof my invention to provide a scanning arrangement which will beparticularly useful for the scansion of facsimiles recorded on narrowbands of tape.

In facsimile transmission known to the prior art it has been customaryto develop a continuous signal, and this signal is then chopped, asillustrated in United States Patent #1389587 granted January 20, 1931,as exemplary of chopping apparatus, and the result is a series ofmodulated pulses. According to the present invention the chopping isaccomplished by the scanning element per se, thus minimizing the amountof equipment necessary.

Also at the present time facsimile transmissions of the tape type havefound interest for such as the transmission of orders to police cars.and particularly at the present-time it is findin interest in thetransmission of intelligence to and from aircraft and particularlymilitary aircraft.

My invention, in general, contemplatesthe use of a transparent ortranslucent tape on which is recorded or marked the intelligence to betransmitted. This tape is passed between a. light masking arrangementwhich admits a slit of light which (Cl. 178-73) My invention relates. ingeneral, to devices for passes normally through the tape and a scanningarrangement. The scanning arrangement consists in a small cylindricalmember having cut through the surface thereof a plurality of small holesspaced apart a short distance from. each other and the entire groupforming a spiral around the periphery of the cylinder of either 360 or180, asmay bedesired. Positioned inside the cylindrical arrangementwhich is rotated is a photocelland, as the cylinder is moved, there willbe developed a chopped tone due to the spacing of the holes or aperturesfrom each other Referring to Fig. 1, there is shown in elevation aschematic arrangement of a transmitter according to my invention. Inthis figure a supply roll it of a thin narrow transparent or translucenttape is provided and is fed through guide rollers ll into contact with aplate I 2.- The intelligence to be transmitted ma be written on the tapeor recorded on the tape in a suitable fashion at this stage of thetransmission. The

tape passes thence through guide rollers 13 and the tape I I is loopedas illustrated and passes thence between guide rollers it. A source oflight it is provided which passes through lens I! and thence through anaperture in a masking arrangement consisting of elements 18 and it. Suchmasks are well known per se, and accordingly will not be described indetail here, but all that is necessary is that the mask will admit andallow to pass therethrough a strip of light which. in general, shouldconsist of a sti'ipof the width of a scanning line of the intelligenceto be scanned.

Positioned adjacent the masking arrangement and spaced apart therefromis the scanning cylinder 20 having a plurality of apertures cut throughthe outer surface thereof, andwhich will be described and, illustratedin greater detail hereinafter in the description of Fig. 2. Positionedon the inside of the cylinder is a photocell 2| having the anode thereofpositioned so as t any aperture in the scanning cylinder which comeswithin the path of the slit 01' light. Signals from the photocell arepassed to appropriate amplifying means. The tape on which theintelligence is recorded is passed between the masking arrangement andthe'scanning cylinder so that portions of the slit of light will beblocked by the opaqueness o! the intelligence recorded on the tape.Hence, as the cylinder is moved the holes will progress steadily acrossthe slit of light which has been intercepted in part by the material onthe tape, and rotation of the cylinderwili pass the apertures from oneside or the tape to the other so as to scan a single line by thecomplete rotation of the scanning if the apertures are cut so as to forma 360 spiral. Of course, for special purposes a 180 spiral might beutilized, but since the particular length of the spiral is not of theessence of this invention, this particular arrangement need not bediscussed here as to the length of the spiral utilized.

Referring to Fig. 2, there is shown a perspective view of the scanningarrangement. As illustrated in this figure, a driving motor 30 having ashaft 3| has fastened to the shaft thereof the member 20 having acylindrical section and into. the cylindrical section is cut theplurality of holes 32 spaced apart from each other by slight amount andbeing arranged in a spiral form of chopped signals representative of theoptical valuesalong a line of the tape will be transmitted. The tape ismoved forward slowly relatively to the scanning by each aperture and, ingeneral, advances a single line during the time that the cylindricalmember revolves and scans an entire line thereof.

It will be appreciated that an arrangement similar to the presentarrangement for scansion purposes might be used at the receiver as wellSuch an arrangement would be very useful, since around the periphery ofthe cylindrical section.

The light source l6 sends a beam of light through the lens I] and thencethrough the masking means comprising the sections l6 and l9,-and fromthere through the transparent tape and through the aperture in thecylindrical section 20 which at the particular instant happens to beadjacent the slit in the masking means. The light beam passing throughthe masking slit should form a fairly intense linear section of lightwhich is the width of the displacement between the aperture at one endof the spiral and the aperture at the other end of the spiral on thescanning cylinder. This is indicated at 35. The photocell 2| positionedinside the scanning cylinder is indicated with the leads thereofpositioned on the outside and in a readily accessible position. No meanshave been shown for holding the photocell in a particular position, norfor holding the masking means in a particular position, since well knownmeans may be used for this purpose, and since these means do not form apart of the invention perse.

This operation of the device is as follows. The tape containing'theintelligence to be transmitted is passed slowly between the maskingarrange- .ment and the scanning element and a beam of light rplaystherethrough, striking the outer surface of the scanning member 20. Asthe scanning member is rotated a single hole or aperture will appearbetween the photocell and the beam of light passing through the maskingaperture, and the optical value of the elemental section of the tapeadjacent this hole will be transmitted to the photocell and anelectridal impulse developed, As the cylinder member 20 rotates thisaperture will pass out of the: beam, and an opaque section between thisaperture and the adjacent aperture will then interrupt or chop the lightto the photocell. As the rotation continues the next aperture comes into the beam of light at a position adjacent that at which the firstaperture intersected the beam of light, and as this cycle goes onprogressively each aperture will come in to the beam of light andtransmit the optical value of the tape at the particular point at whichit is adjacent thereto. Hence, a set it will be seen that the elementsforming the scanner at the transmitter might, by slight rearrangementand by the use of a modulated light source such as a lamp rather than aphotocell, be utilized as a receiver and thus the two arrangements mightalmost be completely.interchangeable.

Referring to Fig. 3, there is shown a partial view of the tubular member20. In this view the tubular member has been cut and has been broughtinto the plane of the paper and the section illustrated hereinrepresents that section which would be seen-where the spiral aperturesbegin and end. In this illustration 9. full 360 spiral has been used.The numerals on the left hand side refer to inches and actually atubular member of approximately four inches in circumierence has beenfound to be very practical. As shown, there might be provided twentyscanning apertures, each aperture being two hundredths by one tenth ofan inch. If this be done and the tubular member is revolved at the rateof sixty revolutions per second, there will be a 1200 cycle sub-carrierdeveloped and the signal de-.

one hundredth of an inch in diameter and the tubular member was revolvedat the rate of sixty revolutions per second, there would be developed a6,000 cycle sub-carrier. Such a design as this would be used in a casewhere the transmission was to comprise D. C. impulses or sub-carrierfrequency modulation. The 6,000 cycle carrier would permit stablealternating current amplifiers to be used in conjunction with the phototube and the signal could be subsequently rectified to give well formeddirect current impulses to control, for example, a frequency modulator.Present practice has tended toward sub-carrier frequency modulation,particularly for use with so-called tape facsimile transmissions.

It will be appreciated that there may be other departures which willfall fairly within the spirit and scope of my invention, and I claim allsuch departures falling fairly within my invention as identified in thehereinafter appended claims.

What I claim is: a

1. The method of scanning an optical image including the steps ofdeveloping signals representative of the optical value of an elementalsection of the image, interrupting the development of the signals for atime period substantially commensurate with the period of signaldevelopment, and developing signals representative of an additionalelemental area after each interruption,

whereby light values are translated into electric frequency measured bythe rate at which the signals are developed and interrupted.

2. Apparatus for developing electrical signal energy indicative of thevariations of light intensity of elemental areas of an optical image.edge of the tubular'member, means for projecting an optical image uponthe tubular member through the slot in the masking element, a lighttranslating element positioned to receive the light of the optical imageas projected through the slot in the masking element and individualapertures of the tubular member to translate said light values intoproportional strength electric currents, and means for rotating thetubular member relative to the masking element so that the I currentssuperimposed upon a predetermined tone width of the slot is scanned bythe said apertures and simultaneously a predetermined chopper frequencyis generated due to the revealing and eclipsing of the light from thelight translating element.

3. Apparatus for developing recurring electrical.

signals indicative of the optical values of an optical image, comprisinga source of light, a tubular member having a plurality of spacedapertures arranged helically around the periphery of said tubularmember, masking means positioned for admitting therethrough a beam oflight of elemental width, means for directing the optical image to bescanned between said tubular member .and said source of light, means.for rotating said tubular member, and photoelectric means positioned soas to have light from said beam of light within the field of said beamof light and representative of said optical values directed by saidtubular means onto said photoelectric means.

4. Apparatus for developing recurring electrical signals indicative ofthe optical values of an optical image, comprising a source of light, atubular member having a plurality of spaced apertures in the peripherythereof, masking means positioned for admitting therethrough a beam oflight of elemental width, means for directing the optical image to bescanned between said tubular member and said source of light, means forrotating said tubular member, and photoelectric means positioned withinsaid tubular member so as to have light from said beam of light withinthe fleld oi said beam of light directed by said tubular means onto saidphotoelectric means and wherein light representative of said opticalvalues is directed onto said photoelectric means by the pas-- sage ofthe apertures in said tubular member sequentially through the beam oflight.

. CHARLES J. YOUNG.

